INTRODUCTION: Appropriate stroke risk stratification is essential to ensure suitable tailoring of antithrombotic therapy. The objective of this study was to assess the predictive value of stroke risk classification schemes and to identify patients with atrial fibrillation (AF) who are at substantial risk of stroke despite optimal anticoagulant therapy, in a "real world" consecutive elderly AF cohort.METHODS: Six hundred and sixty-two consecutive AF patients (mean [SD] age 74 [7.7] years; 36.1% female) referred to the Anticoagulation Clinic of the Azienda Ospedaliera Careggi of Florence, Italy, were included and followed-up for a mean 3.6 ± 2.7 years for the incidence of thromboembolic (TE) events. The ability of the new CHA(2) DS(2) -VASc schema to predict TE was compared with other contemporary stroke risk schema (including CHADS(2) , NICE 2006, ACC/AHA/ESC 2006, and ACCP 2008), by determining the c-statistic.RESULTS: Univariate predictors of TE events were female gender (odds ratio 1.9; 95%CI [confidence intervals] 1.01-3.70) and previous stroke/transient ischemic attack (TIA)/TE (OR 5.6; 95%CI 2.70-11.45), although after adjustment only previous stroke/TIA/TE was an independent predictor of TE (OR 5.5; 95%CI 2.68-11.31; P = 0.0001). All stroke risk schema had modest discriminating ability, with c-statistics ranging from 0.54 (atrial fibrillation investigators [AFI]) to 0.72 (CHA(2) DS(2) -VASc). The CHADS(2) and CHA(2) DS(2) -VASc schemes having the best c-statistics (0.717 and 0.724, respectively) with significant discriminating value between risk strata (both P < 0.001). The proportion of patients assigned to individual risk categories varied widely across the schema, with those categorized as "moderate-risk" ranging from 5.3% (CHA(2) DS(2) -VASc) to 49.2% (CHADS(2) -classical).CONCLUSION: In this "real world" cohort, current published risk schemas have modest predictive ability, with the CHADS(2) and CHA(2) DS(2) -VASc schemes having the best predictive value for thromboembolism. Future trials could assess the value of alternative strategies for thromboprophylaxis in high-risk anticoagulated patients identified by these schemes.